Grade 12 physical science isomers topic, caps approved isomers grade 12, isomers

1. WHAT ARE THEY?
THESE ARE MOLECULES THAT HAVE THE SAME
MOLECULAR FORMULA BUT HAVE A DIFFERENT
ARRANGEMENT OF THE ATOMS IN SPACE.
THAT EXCLUDES ANY DIFFERENT ARRANGEMENT ARRANGEMENTS
WHICH ARE SIMPLY DUE TO THE MOLECULE ROTATING AS A WHOLE OR
ROTATING ABOUT PARTICULAR BONDS.
TYPES OF STRUCTURAL ISOMERISM
1. CHAIN ISOMERISM
2. POSITION ISOMERISM
3. FUNCTIONAL GROUP ISOMERISM

2. 1. CHAIN ISOMERISM
THESE ISOMERS ARISE BECAUSE OF THE POSSIBILITY OF BRANCHING IN
CARBON CHAINS.
FOR EXAMPLE THERE ARE TWO ISOMERS OF BUTANE.
Q: BY THE WAY, WHAT IS ITS MOLECULAR FORMULAE?
IN THE FIRST ISOMER, THE CARBON ATOMS LIE IN A “STRAIGHT CHAIN”
WHEREAS IN THE OTHER, THE CHAIN IS BRANCHED.
LEARNER ACTIVITY: DRAW THE TWO POSSIBLE STRUCTURES.
N.B. BE CAREFUL NOT TO DRAW “FALSE” ISOMERS WHICH ARE TWISTED
VERSIONS OF THE ORIGINAL MOLECULE.

4. 2. POSITION ISOMERISM
THE BASIC CARBON SKELETON REMAINS UNCHANGED, BUT IMPORTANT
GROUPS ARE MOVED AROUND ON THAT SKELETON.
e.g. THERE ARE TWO STRUCTURAL ISOMERS WITH THE MOLECULAR
FORMULA C3H7Br. IN ONE OF THEM, THE BROMINE ATOM IS ON THE END
OF THE CHAIN, WHEREAS IN THE OTHER, ITS ATTACHED IN THE MIDDLE.
ANOTHER SIMILAR EXAMPLE OCCURS IN ALCOHOLS SUCH AS C4H9OH OR

5. 3. FUNCTIONAL GROUP ISOMERISM
THE ISOMERS CONTAIN DIFFERENT FUNCTIONAL GROUPS –
THAT IS THEY BELONG TO DIFFERENT FAMILIES.
EXAMPLES INCLUDE PROPANAL & PROPANONE.
PROPANOIC ACID & METHYL ETHANOATE.
EXTENSION.
Q: DRAW THREE ISOMERS THAT EXHIBIT FUNCTIONAL GROUP
ISOMERISM.